The underlying theme (or hypothesis) of this project is that stress accelerates aging of the reproductive system. Principal methodology involves radioimmunoassay (RIA) of corticosterone, progesterone, androstenedione and prolactin, as well as measures of adrenal response to secretogogues in virto. Preliminary work indicates the 4 hours of chronic stress/day causes cycling female rats to show lengthening of cycle duration. Chronic stress also causes late afternoon levels of prolactin to be elevated 2 days after the day of estrus. The applicant wants to measure in young Fischer rats the corticosterone, ACTH and prolactin responses to acute ether stress and to the shock escape paradigm which is the basis of the chronic stress procedure. These stress procedures will be applied on animals of ages 4, 11 and 18 months to see if there is an effect of age on baseline levels or responses. 4 and 11 month old female rats will be maintained and monitored to assess cyclicity. After 7 months, rats will be maintained and monitored without stress to check for reversibility of loss or lengthening of cycles. These studies will also include a time course of the influence of chronic stress on cyclicity as well as on endpoints studied by other members of the team. Finally, the influence of age and of stress will be assessed on the postovariectomy rise of LH (as well as hypothalamic catecholamine synthesis) and on the ablility of exogenous estradiol to evoke LH surges.